Business entities that provide cloud services using virtual machines (VMs) (hereinafter also called cloud providers) provide cloud services, such as Platform as a Service (PaaS) and Infrastructure as a Service (IaaS), to users who build information processing systems in accordance with their purposes (hereinafter also called cloud users).
Cloud services as mentioned above, for example, are each provided on physical machines deployed in different data centers. Therefore, when an information processing system using a plurality of cloud services is built, communication between cloud services is performed via an outside network (hereinafter also simply called a network), such as the Internet.
Accordingly, a cloud provider, for example, deploys a virtual machine for a gateway (this virtual machine is hereinafter also simply called a GW virtual machine) in each of data centers that provide cloud services, and performs communication between cloud services via a virtual private network (VPN). This enables the cloud provider to ensure the security of communication between cloud services even when a business system using a plurality of cloud services is built (for example, refer to Japanese Laid-open Patent Publication No. 2012-221049 and Japanese Laid-open Patent Publication No. 2014-056335).